1. Field of the Invention
The present invention relates to semiconductor processing equipment. More particularly the present invention relates to isolating one portion of a load chamber from exposure to the surrounding atmosphere when another portion of the load chamber is exposed to the surrounding atmosphere.
2. Description of the Related Art
The processing of silicon wafer substrates in the production of VLSI chips requires an extremely clean environment. Particulate matter, vapor, or impurities that are invisible to the naked eye can substantially decrease production yields if such impurities contact the surface of a substrate during processing. Processing device chambers are designed to control the environment immediately around the wafer substrate and to maintain strict tolerances for cleanliness. Typically, the first chamber in a processing device is an input/output chamber commonly known as the loadlock chamber. The loadlock chamber introduces substrates into the device in a manner that exposes minimal volume and internal surface area to the outside environment. The present invention provides an improved loadlock chamber that results in a decreased exposure of internal surface area to the outside environment.
In one aspect of the present invention, a loadlock chamber for a semiconductor processing apparatus comprises an index platform or registration plate, a shaft extending through a wall of the chamber to actuate the platform, and a bellows located on the outside of the chamber to isolate the shaft from the external environment. A seal is placed between the bottom of the registration plate and the wall of the chamber so as to isolate the space under the registration plate and within the bellows from the remainder of the chamber when the platform is in a fully lowered position. In this manner, the remainder of the chamber can be opened to the external environment without exposing the space within the bellows to contamination. Once the chamber door has been closed and the chamber purged, the registration plate can again be raised to expose the space within the bellows to the remainder of the chamber. Accordingly, the space within the bellows is then safely exposed to an environment that has already been purged of contamination.
In another aspect, the present invention incorporates a gutter formed in a wall of the chamber below the registration plate. The gutter surrounds the edge of the platform and is configured to catch particulate matter, such as broken wafer particles. The gutter prevents the particulate matter from passing under the registration plate, past the seal, and into the bellows.
In another aspect, the present invention provides a method of accessing the interior of a loadlock chamber from outside the chamber. The method limits exposure of the space within the bellows to the external environment. Accordingly, the introduction of contamination into the space within the bellows is reduced.